Threads.hpp

/*
 * This file is part of bogus, a C++ sparse block matrix library.
 *
 * Copyright 2016 Gilles Daviet <gdaviet@gmail.com>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/

#ifndef BOGUS_UTILS_THREADS_HPP
#define BOGUS_UTILS_THREADS_HPP

#include "../Block/Constants.hpp"

#ifndef BOGUS_DONT_PARALLELIZE
#include <omp.h>
#endif

namespace bogus {

#ifdef BOGUS_DONT_PARALLELIZE
    struct WithMaxThreads {
        explicit WithMaxThreads( int ) {}
        int nThreads() const { return 1 ; }
    } ;

#else
    struct WithMaxThreads {

        explicit WithMaxThreads( int maxThreads )
            : m_prevMaxThreads( omp_get_max_threads() )
            ,  m_newMaxThreads( maxThreads == 0 ? m_prevMaxThreads : maxThreads )
        {
            omp_set_num_threads( m_newMaxThreads ) ;
        }

        ~WithMaxThreads() {
            omp_set_num_threads( m_prevMaxThreads ) ;
        }


        int nThreads() const { return m_newMaxThreads ; }

    private:
        const int m_prevMaxThreads ;
        const int m_newMaxThreads ;

    };
#endif

} // bogus

#endif